1. Field of the Invention
The invention relates to the mounting of a reservoir on a master cylinder body, and more particularly to such a mounting when the master cylinder assembly formed by the reservoir and a cylinder body is of the dual master cylinder type.
2. Description of the Prior Art
It has been common practice to manufacture master cylinders with a plurality of pressurizing pistons acting on brake fluid in a plurality of pressurizing chambers which are located in axial alignment in a bore in a cylinder body, or in axially parallel bores in a cylinder body. Examples are shown in U.S. Pat. Nos. 2,157,733 entitled "Brake", issued May 9, 1939; 2,732,918 entitled "Brake Master Cylinder Assembly", issued Jan. 31, 1956; 3.021,678 entitled "Master Cylinder for Fluid Brake System", issued Feb. 20, 1962; 3,157,034 entitled "Dual Master Cylinder", issued Nov. 17, 1964; and 3,291,263 entitled "Servo Actuated Disc Brakes", issued Dec. 13, 1966, as well as the other patents noted below. In order to provide a separate reservoir body for brake fluid, reservoirs have been attached to the cylinder body in more recent years by means of a projection and a boss or mounting bore for each bore or bore section having a pressurized chamber. Examples of such arrangements are shown in U.S. Pat. Nos. 4,004,707 entitled "Fluid Baffle in Master Cylinder Reservoir", issued Jan. 25, 1977; 4,132,073 entitled "Master Cylinder Assembly" issued Jan. 2, 1979; 4,133,178 entitled "Quick Take-Up Master Cylinder", issued Apr. 18, 1979; 4,133,287 entitled "Reservoir With Integrally Formed Window and Method of Making Same", issued Jan. 9, 1979; 4,208,881 entitled "Quick Take-Up Master Cylinder", issued June 24, 1980; and 4,213,535 entitled "Fluid Reservoirs for Master Cylinders", issued July 22, 1980. In general, these arrangements have two or more openings which are spaced apart in the bottom of the reservoir body, which may or may not be connected to a spigot or bayonet formed or secured to the bottom of the reservoir body, which fit over or extend into bores formed in similarly spaced apart bosses which are a part of a cylinder body. Openings through the bayonets and the cylinder body bosses permit brake fluid to flow between the bore or bores of the master cylinder body and the reservoir in a manner well known in the art.
In order to assure that the master cylinder reservoir will always be assembled properly into or on the master cylinder body, the diameters of the openings formed in the bottom of the reservoir, as exemplified by U.S. Pat. No. 4,004,707 noted above, or of the bayonets and their seals, as exemplified by the other patents thereafter noted above, must be so sized as to accommodate all of the tolerances along the centerline joining the two bores in the cylinder body bosses as well as the tolerances in the associated portions of the reservoir body itself. Therefore, the basic diameters of the bayonets must be sufficiently small in relation to the bosses or opening with which they mate to accommodate what is commonly known as worst case tolerancing, or openings fitting over bosses must be sufficiently larger. Because of these differences in diameters, there is often excessive clearance which allows the reservoir body to fit somewhat loosely on the cylinder body, particularly insofar as the side-to-side relationship is concerned.
It is therefore desirable to minimize the excessive side-to-side clearance by better matching the diameter of the bayonet, for example, in the master cylinder mounting bore with which each bayonet is associated, rather than having to allow for worst case tolerancing involving both of the reservoir mounting bores and both of the mounting bayonet members, or even more such bores and bayonet members if three or more such combinations are provided. Such considerations include not only the individual diameters of each such arrangement but also the axial spacing between such plurality of arrangements. Since the worst case tolerancing must be considered in the plane joining the axes of the bosses and bayonet members, the diameters cannot be increased in this plane as would otherwise be desired.